LED High Bay vs Metal Halide — ROI, lumen/W, and Replacement in Thai Factories

Factory lighting over 5,000-50,000 m² accounts for 15-30% of the total electricity bill — it is the fastest place to save if you switch from old Metal Halide (HID) to LED High Bay. ROI of 12-24 months is normal in Thailand — especially in warehouses + secondary production halls that run lights continuously. This article compares the numbers per IEC 60598 + IES TM-21 + DALI standard.

Main Table — LED High Bay vs Metal Halide

TCO Comparison — 100-luminaire factory, 12 hr/day, 6 days/week

Thai TOU electricity: Peak average 4.50 baht/kWh, off-peak 2.85 baht/kWh — blend 3.75 baht/kWh

flowchart LR
  A[100 high bay luminaires
factory] --> B{Existing
Metal Halide 400W?}
  B -->|Yes| C[Annual: 400W × 100 ×
3,744 hr/yr =
149,760 kWh × ฿3.75 =
฿561,600/yr]
  B -->|Retrofit LED 150W| D[Annual: 150W × 100 ×
3,744 hr/yr =
56,160 kWh × ฿3.75 =
฿210,600/yr]
  C --> E[Maintenance:
lamp+ballast
~฿80,000/yr]
  D --> F[Maintenance:
~฿8,000/yr]
  E --> G[Total HID:
~฿641,600/yr]
  F --> H[Total LED:
~฿218,600/yr]
  G --> I[Savings ฿423,000/yr
+ 90% maintenance reduction]
  H --> I

Capital cost for 100 luminaire conversion:

• Full luminaire replacement: 5,000-12,000 ฿/luminaire × 100 = 500,000-1,200,000 baht
• Installation labor + scaffold: ~150,000-300,000 baht
• Total CAPEX: 650,000-1,500,000 baht

Payback period:

• Lowest case: ฿650,000 / ฿423,000 = 1.5 years
• Highest case: ฿1,500,000 / ฿423,000 = 3.5 years
• Median: 2-2.5 years

After payback: ฿423,000/year × 7-8 more years = ฿3-3.4 million NPV savings over 10 years

Flowchart — Selecting Wattage by Mounting Height

flowchart TD
  A[Define requirement] --> B{Lux requirement?}
  B -->|General warehouse
200-300 lux| C[Standard wattage]
  B -->|Assembly line
500-750 lux| D[Higher wattage]
  B -->|QC / Inspection
750-1000 lux| E[Highest wattage + supplemental]
  C --> F{Mounting height?}
  D --> F
  E --> F
  F -->|4-6 m| G[100-150W LED
15,000-22,500 lm]
  F -->|6-9 m| H[150-200W LED
22,500-30,000 lm]
  F -->|9-12 m| I[200-240W LED
30,000-36,000 lm]
  F -->|> 12 m| J[300W+ LED
or spot beam optic]
  G --> K[Spacing 8-10 m
general square grid]
  H --> K
  I --> K
  J --> K
  K --> L[Verify with Dialux
or AGi32]

IEC 60598 + IES TM-21 — Standard Compliance

A LED High Bay that meets the standards must have:

• IEC 60598-1 — General safety (insulation, mechanical, thermal)
• IEC 60598-2-22 — Emergency luminaire (if used as emergency)
• IEC 62717 — Performance requirements for LED modules
• IEC 62722-2-1 — Performance of LED luminaires
• IES LM-79 — Total flux + electrical + color measurement
• IES LM-80 — Lumen maintenance of LED package (long-term test)
• IES TM-21 — Projects LED long-term lumen output (uses LM-80 data extrapolated)

Common Rated Life metrics:

• L70 — time at which lumens remain at 70% of initial (= 50,000 hours typical)
• L80 — time at which lumens remain at 80% (= 30,000-40,000 hours)
• L90 — time at which lumens remain at 90% (= 15,000-25,000 hours)

Factories use L80 or L70 as mainstream. Rooms requiring color consistency (printing, QC) use L90

Light Distribution Pattern — Choosing the Right Optic

Commonly used beam angles:

• 60-90° — square grid spacing 8-10 m
• 100-120° — square grid spacing 10-12 m
• 30-60° — high ceiling > 10 m + accent spotlight

IP Rating + Environment

Thai factories come in many conditions — choose the IP rating to match reality:

• IP20 — sealed ceiling, dust-free (electronic clean room)
• IP44 — splash water from any direction (kitchen, food processing — wash-down)
• IP54 — dust protected + splash (general factory)
• IP65 — dust tight + low pressure jet (warehouse with forklift dust)
• IP66 — dust tight + high pressure jet (outdoor, daily wash-down)

Typical Thai factory → IP65 is the safe standard. Outdoor / wash-down → IP66

Lighting Control — DALI vs 0-10V vs Bluetooth Mesh

DALI is the international standard for professional lighting:

• Address individual luminaires (one at a time)
• Group + scene programming
• Sensor input (occupancy, daylight)
• Energy reporting for each luminaire
• Automatic fault detection

Energy savings from control:

• Manual switching: 0%
• 0-10V scheduling: 10-15%
• DALI + occupancy + daylight: 30-40%
• DALI tuned + adaptive: 40-50%

Replacement Cost Risk + Warranty

The driver (electronic ballast) usually fails 2-3× before the LED chip. The driver costs ~30-40% of the luminaire. A budget brand with a 1-year warranty = risk of replacement from year 2 onward — TCO may be worse than premium

6-Point Procurement Guidelines

1. TOR specifies IEC 60598-1 + IEC 62717 + IES LM-79 + LM-80 + L70 ≥ 50,000 hours
2. CRI ≥ 80 + Color Temperature 4000K for general factory work
3. IP65 minimum for industrial environments
4. DALI or 0-10V dimming compatible for future upgrade
5. Warranty ≥ 5 years including driver + LED module — written contract clause
6. Photometric file (IES file) from the supplier to verify with Dialux/AGi32 before ordering

Conclusion

LED High Bay replacing Metal Halide in Thai factories delivers a payback of 1.5-3.5 years + savings of 60-70% on electricity + 90% reduction in maintenance. L70 ≥ 50,000 hours + CRI ≥ 80 + 4000K Natural White are the standard. IP65 for industrial. DALI control pays off for systems > 50 luminaires. Premium brands (Philips, Osram, Eaton) with 5-7 year warranties — better TCO than budget brands even though the initial price is 50-100% higher.

Sahawatthanakit provides lighting audit + retrofit design + Dialux simulation + installation for factories of 50-500 luminaires — consult us for an ROI calculation based on your actual size and operating conditions.

Frequently Asked Questions

What is the payback period? In a Thai factory running lights 12-16 hr × 6 days — a LED 150W replacing a MH 400W → payback 12-24 months. DALI dimming reduces it another 20-30%

How much do Lumens/W differ? MH initial 65-95 lm/W, dropping to 40-60 after 5,000 hr. LED 2026 initial 150-200, retaining 80%+ after 50,000 hr. A 2-3× difference throughout the lifetime

Which Color Temp to choose? General + warehouse 4000K. QC/inspection 5000-5700K CRI≥80. Food 4000K CRI≥80. Don't use 6500K+ — eye strain. Don't buy CRI < 70

How does Mounting Height matter? 6 m → 150W (22,500 lm) covers 75-100 m². 8-10 m → 200-240W. Calculate with Dialux/AGi32

DALI vs 0-10V? 0-10V analog is cheap, group dimming. DALI digital, addressable per luminaire + scheduling + sensor integration. Pays off for > 50 luminaires

Retrofit lamp vs Full replacement? Retrofit lamp is cheap but the old ballast draws 10-15W + poor thermal → short life. Full replacement is better with 5-year warranty + IP65 + driver efficiency — recommended for > 50 luminaires